【摘要】：濕法制備多晶硅太陽電池表面絨面結構，實際上是溶液中離子和多晶硅相互作用的過程，但是離子運動一般不可控，導致其腐蝕得到的微結構始終不理想�！半x子泡”有可能改變這一現(xiàn)象�！半x子泡”實際上是在濕法腐蝕過程中利用超聲產(chǎn)生的微氣泡表面帶電特性吸附離子，形成“離子+泡”結構，從而可以實現(xiàn)離子的可控。但是對于這一模型研究依賴于對超聲產(chǎn)生的微氣泡帶電特性機理的研究，目前這方面還缺乏定性研究。為此首先要展開對超聲微泡裝置研究，為日后超聲微氣泡特性研究打下基礎。 首先，，對超聲氣泡產(chǎn)生過程進行了分析，并根據(jù)超聲在水中產(chǎn)生空穴的所需要的聲壓條件計算模型出發(fā)，分析了相關因素對超聲氣泡形成過程，以此為基礎設計了超聲微氣泡的發(fā)生裝置。 其次，對超聲系統(tǒng)機械部分進行了設計，分別用等效電路法設計和傳統(tǒng)解析法確定了超聲換能器和變幅桿的機械參數(shù)。為保證設計的可靠性，文中對設計的變幅桿進行了有限元模擬。運用模態(tài)分析得出其固有諧振頻率和設計工作頻率之間誤差在允許范圍之內(nèi)，運用諧響應分析得出其端面輸出位移和最大應力要求也均滿足設計要求。 然后利用FLUNENT軟件建立了超聲微泡發(fā)生器數(shù)學計算模型及賦予相應的初始邊界條件，對各種可能影響氣泡生成效果的因數(shù)進行數(shù)值模擬。文中重點模擬了超聲功率、氣孔孔徑、氣體種類、變幅桿結構等影響。通過流場的模擬得出，超聲功率對氣泡的影響最為顯著，在無功率以及低功率的條件下，只會產(chǎn)生宏觀的氣泡；同時氣孔孔徑影響在于與超聲功率協(xié)調(diào)性；從模擬的結果上看氣體種類對微氣泡產(chǎn)生的影響不顯著；在模擬中更改了發(fā)生器的結構，將其由平面型結構改成凹球面結構，模擬結果說明這種結構對流場的壓力有顯著的加強過程，而這種壓力對流場局部作用明顯，對于氣泡產(chǎn)生過程也有較大的影響。 最后，開展了超聲氣泡發(fā)生器實際效果測試實驗，測試實驗中主要就功率對氣泡產(chǎn)生情況進行分析，得出結果和實際模擬結果可以很好的符合。通過利用高速攝影機得到照片結果分析得到，可以產(chǎn)生微米級的氣泡。 通過論文研究，初步實現(xiàn)了超聲微氣泡裝置的研究，并通過二相流的模擬得出氣泡生成過程中影響關鍵因素。這為后期進一步研制可控大小、可控數(shù)目微氣泡用于超聲微氣泡特性研究提供了依據(jù)。
[Abstract]:Wet fabrication of surface suede structure of polycrystalline silicon solar cells is actually a process of interaction between ions and polysilicon in solution, but the ion movement is generally uncontrollable, resulting in the microstructure obtained by corrosion is always not ideal. Ion bubbles may change this phenomenon. In fact, "ion bubble" is used to adsorb ions on the surface of micro-bubble produced by ultrasonic in the process of wet corrosion, forming "ion bubble" structure, so that the ion can be controlled. However, the study of this model depends on the study of the mechanism of charge characteristics of microbubbles produced by ultrasound, which is still lack of qualitative research. Therefore, the research of ultrasonic microbubble device should be carried out first, which will lay a foundation for the study of ultrasonic microbubble characteristics in the future. Firstly, the process of ultrasonic bubble formation is analyzed, and based on the model of sound pressure conditions needed to generate holes in water, the relevant factors are analyzed. Based on this, a device for generating ultrasonic microbubbles is designed. Secondly, the mechanical part of ultrasonic system is designed, and the mechanical parameters of ultrasonic transducer and amplitude bar are determined by the method of equivalent circuit and the traditional analytical method. In order to ensure the reliability of the design, finite element simulation of the designed horn is carried out in this paper. The error between the inherent resonance frequency and the design working frequency is found to be within the allowable range by modal analysis, and the output displacement and maximum stress requirements of the end face are also satisfied by the harmonic response analysis. Then the mathematical calculation model of ultrasonic microbubble generator and the corresponding initial boundary conditions are established by using FLUNENT software. The various factors that may affect the effect of bubble formation are simulated numerically. The effects of ultrasonic power, pore aperture, gas type and amplitude-varying bar structure are simulated. Through the simulation of flow field, it is concluded that ultrasonic power has the most significant effect on bubbles, and only macrobubbles can be produced under the condition of no power and low power, meanwhile, the influence of pore aperture is the coordination with ultrasonic power. From the result of simulation, the effect of gas type on microbubble is not significant. In the simulation, the structure of generator has been changed from plane structure to concave spherical structure. The simulation results show that the pressure of the flow field of this kind of structure has a significant strengthening process, and the local effect of this pressure flow field is obvious, which also has a great influence on the bubble production process. Finally, the practical effect test experiment of ultrasonic bubble generator is carried out. In the test experiment, the power of the bubble is analyzed, and the results are in good agreement with the actual simulation results. By using the high speed camera to get the result of the photo, the micrometer bubble can be produced. Through the research of this paper, the research of ultrasonic micro-bubble device is realized, and the key factors of bubble formation are obtained through the simulation of two-phase flow. This provides a basis for the further development of controllable size and number of microbubbles for the study of ultrasonic microbubbles.
【學位授予單位】：杭州電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM914.4;TB559

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